In a liquid crystal display or a projection display using a liquid crystal element, a decrease in contrast and occurrence of color shading, due to characteristics of angle of visibility and phase retardation of the liquid crystal element, are well known. These degrade performance of a display. A display has an optical compensator that is an optical component to correct these.
In a liquid crystal display using a horizontally aligned liquid crystal element, an optical compensator is placed parallel to a liquid crystal display substrate. However, to correct optically, it is necessary to make the optical axis of the optical compensator coincide with the pretilt direction of a liquid crystal display element. Therefore, it is necessary to rotate the optical compensator in a surface thereof to adjust and fix it at a most suitable position.
On the one hand, Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-259093) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-338478) disclose technologies that, by rotating a polarizing plate in a surface thereof, the polarization axis of the polarizing plate coincides with the polarization direction of linear polarization. These technologies can be used to rotate the optical compensator in the surface thereof.
In the technology disclosed in Patent Document 1, a hole in a corner of a second frame for supporting a polarizing plate on the incident side is rotatably engaged with a salient portion projecting from a corner of a first frame fixed on a device main body. Then, rotating a screw provided in a corner opposite to the salient portion can adjust the angle of the polarizing plate on the incident side in the horizontal direction relative to a liquid crystal panel.
In the technology disclosed in Patent Document 2, a holder for supporting a glass plate to which a polarizing plate is adhered is rotatably supported by a member on the fixed side, and rotating the holder can adjust an angle of the polarizing plate on the incident side relative to the liquid crystal panel.
Besides a liquid crystal display using a liquid crystal panel including a horizontally aligned liquid crystal element such as a twisted nematic (TN) type, there is also a liquid crystal display (vertically-aligned-mode liquid crystal display) using a liquid crystal panel including a liquid crystal element having a vertically aligned liquid crystal element.
The vertically-aligned-mode liquid crystal display described above differs from a horizontally-aligned-mode liquid crystal display, as to an alignment of a liquid crystal. Therefore, both a characteristic of the angle of visibility and phase retardation of the liquid crystal element exhibit quite different characteristics from those of the horizontally-aligned-mode liquid crystal display. Accordingly, the vertically-aligned-mode liquid crystal display cannot use the methods for suppressing a decrease in contrast and occurrence of color shading by rotating the optical compensator in the horizontal direction, used in the horizontally-aligned-mode liquid crystal display.
Then, Patent Document 3 (Japanese Patent Application Laid-Open No. 2006-11298) discloses a technology for improving contrast by using an optical compensator that is a wave plate having optically negative uniaxiality (hereinafter, called “optical compensator for vertically-aligned-mode), to correct optically the vertically-aligned-mode liquid crystal display.
FIGS. 1(a), 1(b) show the principle for describing a difference in adjustment methods of an optical compensator corresponding to a liquid crystal panel in a horizontally-aligned-mode and a liquid crystal panel in a vertically-aligned-mode. FIG. 1(a) shows the case of the liquid crystal panel in a horizontally-aligned-mode, and FIG. 1(b) shows the case of the liquid crystal panel in a vertically-aligned-mode.
The liquid crystal panel in a horizontally-aligned-mode, as shown in FIG. 1(a), was adjusted by rotating optical axis A of optical compensator 12 in adjustment direction B in the same surface. On the one hand, in the liquid crystal panel in a vertically-aligned-mode, as shown in FIG. 1(b), optical axis C of optical compensator 11 for vertically-aligned-mode is positioned in the direction perpendicular to alignment direction E of liquid crystal molecules on a surface of a substrate of a vertically aligned liquid crystal element on the light incident side. Then, it is necessary to rotate optical compensator 11 for vertically-aligned-mode around optical axis C in adjustment direction F by an angle corresponding to a pretilt of liquid crystal molecules from a plane parallel to the liquid crystal panel.
As described above, the optical compensator for vertically-aligned-mode has to be placed so that a surface thereof is tilted to an incident surface of the vertically aligned liquid crystal element, which presents the problem that the adjustment mechanism of the optical compensator for horizontally-aligned-mode as disclosed in Patent Documents 1, 2 is not applicable. Further, the adjustment method disclosed in Patent Document 3 is mainly describes about a basic item and a specific configuration of the adjustment means is not sufficiently disclosed.